Foam concrete consists of foam that is added to a mortar mix to produce lightweight structural elements. It is a very efficient technique for producing insulated lightweight structural elements that can be used to cover walls, floors and roofs.

The main role of the foaming agent is to introduce air bubbles into the mixture of cement and aggregate. The foaming agent has a significant effect on the density, porosity, stability and fluidity of foam concrete.

Protein based foaming agents are very important because they allow the formation of a stronger pore structure and a more closed void space network, thereby increasing the compressive strength of foamed concrete. These proteins also help reduce the water absorption rate.

Stability of foams produced by protein and synthetic foaming agents is dependent on a number of factors. The type of aggregate, the amount of water added to the foam mixture and the degree of drying shrinkage are all considered.

The use of recycled concrete aggregate (RCA) in geopolymer foam concrete instead of fine sand significantly improved the foam stability. This was due to the RCA’s high water absorption properties. It also reduced the depth of defoaming and increased the yield strength of the foam concrete.